The present invention relates generally to telecommunication networks, and more particularly, to a method and system for detecting a discontinuous transmission mode of operation of a network.
As shown in FIG. 1, in a common wireless communication network 10, a mobile unit (MU) 12 receives transmitted information from a base transmission station (BTS) 14 through a forward link, and communicates back to the BTS through a reverse link. It is understood that the BTS 14 may be representative of several different components, including a base station controller and a mobile switching center. Modern communication technologies such as CDMA2000 allow a discontinuous transmission (DTX) mode to be operated on a supplemental channel (SCH) for both forward and reverse links. Before the data is transmitted on the supplemental channel, a MU has to reserve the radio resource for that particular channel. This is accomplished via a supplemental channel assignment procedure, during which a set of parameters for the assigned channel is communicated between the MU and BTS. These parameters may include data rate, coding method, frame length and the duration of the assigned channel. The DTX mode allows the transmission to be stopped on the assigned channel before the end of assigned time slot if there is no data to transmit.
There are several problems associated with DTX mode. Some of the problems relate to fading. In a fading environment, a transmitted frame may be erased if the transmission link experiences a deep fade. For a SCH, the MU has to determine the number of erasure frames received. Such a determination provides information for possible adjustment of the transmission power via signaling messages. Thus, the MU needs to determine, without any prior knowledge of the current transmission mode, whether the transmitted frame is erased due to fading or that data was discontinued (the transmitter has entered the DTX mode). An incorrect determination of erasure frames will trigger unnecessary signaling messages between the MU and the BTS. Further, these messages may cause the transmission power level to be raised too high once the transmission resumes.
Therefore, what is needed is a method for accurately detecting the DTX mode from a receiver side so that efficient system performance can be maintained.
Various methods for effectively detecting the discontinuous transmission (DTX) mode are provided both from the physical layer perspective and from the medium access layer (MAC) perspective. These methods can work together and/or individually. Furthermore, certain features of different methods can be combined in various manners. One embodiment provides a method for detecting the DTX mode transmission on reverse supplemental channels by comparing the transmitted and the received power ratio of a pilot channel and a supplemental channel. Another embodiment detects the DTX mode transmission on a dedicated control channels on the reverse link.
In some embodiments, the DTX mode transmission on a forward link supplemental channel is detected. The transmitted and received power ratios of a primary power control channel and the supplemental channel are monitored to indicate that the DTX mode is being entered by a base transmission station (BTS).
In some embodiments, a new parameter to the MAC layer is provided. The parameter indicates to the receiver that the transmitter has entered into the DTX mode.
Any of the disclosed embodiments provides a reliable way to detect the DTX mode. Reliable detection of DTX mode saves the transmitter power and reduces the interference level in the cell. More importantly, improper operations of the BTS and a mobile unit (MU) are avoided, and thus the rate for call drop is reduced. Therefore, the present invention enhances the efficiency and reliability of BTSs.